Stamping or embossing machines usually have at least one and often a plurality of guide rollers for guiding a web of material as it passes through the machine, the roller or each thereof being supported by means of a ball bearing assembly. Guide rollers of that kind entail such a level of friction that it is only possible to achieve machine speeds of 200 meters per minute. Due to friction, thin narrow foil webs may suffer from unacceptable stretching or in an extreme case may even be damaged to such an extent as to be effectively ruined.
Reference may be made to U.S. Pat. No. 3,349,462 disclosing a guide roller which is intended for use in a textile machine, that is to say for guiding or changing the direction of a textile web as it passes through the machine. The roller has a roller spindle which is fixed with respect to the support structure of the machine, and a porous air-permeable spindle sleeve is fixed to the roller spindle, with the axially remote end portions of the spindle sleeve. A roller sleeve is in turn supported on the spindle sleeve, and the roller spindle has a compressed air passage for supplying the spindle sleeve with compressed air which is operative to form an air cushion between the spindle sleeve and the roller sleeve. It will be noted here that textile webs usually enjoy a relatively high level of mechanical strength so that there is no real fear of friction-induced unacceptable stretching or elongation of the web material, in particular during the phase of starting up the machine. The situation is different when dealing with thin narrow stamping foil webs.
Reference may also be made to DE 44 16 421 A1 disclosing a heatable and coolable roller which is suitable for transporting materials in web form and for providing temperature control in respect thereof. The roller disclosed therein is distinguished by an extremely low level of bearing friction. To support the roller casing which rotates on a fixed cylindrical core, that roller arrangement uses a fluid which flows predominantly in a peripheral direction between the roller casing and the roller core. The fluid can be used at the same time to provide for temperature control of the roller casing. As the fluid used for temperature control flows preferably in the peripheral direction in the region of the usable roller width, that provides for excellent constancy of temperature over the width of the roller.